SPIRIFERIDtE. 



127 



those of individuals ; but as I could not satisfy myself that such was really the case, it 

 wUl be better provisionally to describe B. 'Baylei and B. Bouchardii, if not as separate 

 species, at least as subspecies or varieties. 



Position and Locality. Abundant in the Wenlock limestone of Sedgley, Wenlock 

 Edge, and Benthall Edge ; Dudley ; at Hay Head, near the Rushall Canal, Walsall ; 

 Malvern and May Hill ; and in the Ludlock rocks near Llandeilo. 



It has also been found in the Island of Gothland by Lindstrom, and at Lode, Kasti, 

 Sandel, Kaugatoma-Pank, Ohhesaare-Pank, &c., in the Baltic Provinces, by Prof. F. 

 Schmidt. 



Var. R. Baylei, Davidson. PI. XII, figs. 23, 24, 25, and 27. 



Terebratula Baylei, Bav. Bull. Soc. Geol. France, vol. v, '2nd ser., p. 330, 

 pi. iii, fig. 29, 1848. 



Retzta Salteri, var. Baylei, Salter. Siluria, 2nd edit., p. 250, Foss. 57, fig. 8, 1859. 



Circular, or a little longer than wide, greatest width about the middle ; sides rounded, 

 very slightly indented in front ; valves almost equally convex ; beak small, pointed, 

 incurved, with the foramen situated under its angular extremity, and margined by a 

 deltidium in two pieces. Valves ornamented with from eleven to fifteen ribs, of which 

 the central one in the dorsal valve is by far the narrowest, Avhile two small ribs extend 

 along the narrow sinus in ventral valve. Valves crossed by concentric lines, and minute 

 spinular asperities cover the surface. Two specimens measured — 

 Length 4, width 4, depth 3 lines. 

 4, „ 5, „ 4 „ 



Position and Locality. It is common in the Wenlock limestone in all the localities in 

 which B. Salteri occurs, and is most likely a dwarfed variety of that shell. 



Var.? R. Bouchardii, Davidson. PI. XII, figs. 26, 28—30.^ 



Terebratula Bouchardii, Dav. Bull. Soc. Geol. France, vol. v, 2nd ser,, p. 332, 

 pi. iii, fig. 38, 1848. 



Retzia — Salter. Siluria, 2nd edit., p. 250, Foss. 57, fig. 4, 1859. 



Transversely or elongated oval ; sides rounded, slightly indented in front. Valves 

 almost equally convex ; beak in the ventral valve small, incurved, and truncated by a 

 small circular foramen, partly margined by a short deltidium in two pieces. Valves 

 ornamented with from twenty-one to twenty-nine small angular ribs, of which the two or 

 four central ones in the dorsal valve are much smaller or narrower than those on the 

 lateral portions of the valve, and they occupy a slightly lower level. In the ventral valve 



